An Electrochemical Cell Coupled with Disposable Screen-Printed Electrodes for Use in Flow Injection Analysis

Screen-Printed Technologies Combined with Flow Analysis Techniques: Moving from Benchtop to Everywhere

Screen-printed electrodes (SPEs) coupled with flow systems have been reported in recent decades for an ever-growing number of applications in modern electroanalysis, aiming for portable methodologies. The information acquired through this combination can be attractive for future users with basic knowledge, especially due to the increased measurement throughput, reduction in reagent consumption and minimal waste generation. The trends and possibilities of this set rely on the synergistic behavior that maximizes both SPE and flow analyses characteristics, allowing mass production and automation. This overview addresses an in-depth update about the scope of samples, target analytes, and analytical throughput (injections per hour, limits of detection, linear range, etc.) obtained by coupling injection techniques (FIA, SIA, and BIA) with SPE-based electrochemical detection.

Single amino acid utilization for bacterial categorization

Despite great advancement in genetic typing, phenotyping is still an indispensable tool for categorization of bacteria. Certain amino acids may be essential for bacterial survival, growth, pathogenicity or toxin production, which prompts the idea that the intrinsic ability to utilize single amino acid under live-or-die situation could be a basis for differentiation of bacteria species. In this study, we determined the single amino acid consumption profiles of 7 bacterial species, and demonstrated that most bacteria have species-specific pattern of amino acid consumption. We also discovered that bacterial strains from different hosts, toxigenicity, and antibiotic-resistance presented distinct preference for certain amino acids. Taken altogether, the amino acid consumption profiles showed potential to be a novel tool complementary to study not only bacterial categorization but also biochemical characteristics of the bacteria such that its phenotyping can be used to uncover strategies for nutritional, pharmaceutical, taxonomic, and evolutionary aspects of bacterial researches.

Synthesis, structure and cation-binding properties of some [4 + 4] metallocyclic MO2(2+) (M = Mo or W) derivatives of 9-phenyl-2,3,7-trihydroxyfluor-6-one

The trianion Z(3-) obtained from 9-phenyl 2,3,7-trihydroxyfluor-6-one, ZH3, affords dioxomolybdenum and dioxotungsten derivatives which contain [4 + 4] metallocycles of composition [(MO2)4Z4](4-) (M = Mo, W) in combination with a variety of counter cations. The syntheses, structures and ESMS of the following compounds are presented: compound 1, (MePPh3)3(NBu4)[(MoO2)4Z4]; compound 2, (MePPh3)3(NBu4)[(WO2)4Z4]; compound 3, (MePPh3)4[(WO2)4Z4]; compound 4, (PPh4)2(NBu4)2[(MoO2)4Z4]; compound 5, (AsPh4)3(NBu4)[(MoO2)4Z4]; compound 6, (AsPh4)2(NBu4)2[(WO2)4Z4]; compound 7, (Ph3PNPPh3)(NBu4)3[(MoO2)4Z4]; compound 8, (Ph3PNPPh3)(NBu4)3[(WO2)4Z4]; compound 9, (NEt4)(NBu4)3[(MoO2)4Z4]. The metallocycles in all of these compounds have similar structures, with the four metal centers located at the corners of a square slightly distorted, to varying degrees, toward a rhombus and also toward a tetrahedron. Various cations are bound inside the anionic metallocycles. ESI mass spectrometry shows that the metallocycles remain intact in the gas phase, forming [(MO2)4Z4](4-), {X-[(MO2)4Z4]}(3-) and in some cases {X2-[(MO2)4Z4]}(2-) where X(+) is an organic cation.

Spectrophotometric determination of hydrogen peroxide with osmium(VIII) and m-carboxyphenylfluorone

Spectrophotometric determination of hydrogen peroxide was accomplished with osmium(VIII) and m-carboxyphenylfluorone (MCPF) in the presence of cetyltrimethylammonium chloride (CTAC). In the determination of hydrogen peroxide based on the fading of the color of osmium(VIII)-MCPF complex, Beer's law was obeyed in the range 20-406 ng mL(-1), with an effective molar absorption coefficient (at 580 nm) of 5.21×10(4) L mol(-1) cm(-1) and a relative standard deviation of 0.33% (n=6). Further, we performed the characterization of MCPF and obtained the crystal structure.

Simultaneous detection of NADH and H₂O₂ using flow injection analysis based on a bifunctional poly(thionine)-modified electrode

We report here a novel detection scheme for simultaneous detection of NADH and H(2)O(2) based on a bifunctional poly(thionine)-modified electrode. Electropolymerization of thionine on a "preanodized" screen-printed carbon electrode effectively lowers the oxidation potential of NADH to 0.15 V (vs. Ag/AgCl). Since poly(thionine) is also a well known electrochemical mediator for H(2)O(2) reduction, we further developed a poly(thionine)-modified ring disk electrode for simultaneous measurement of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)) by flow injection analysis. By applying the optimized detection potentials of 0.2V and -0.2V at disk and ring electrodes, respectively, this system allows the simultaneous measurement of both analytes with good sensitivity (0.13 μA/mM for H(2)O(2) and 0.34 μA/mM for NADH) and limit of detection (1.74 μM and 26.0 μM for NADH and H(2)O(2)). This opens the possibility of a whole series of biosensor applications.